When an extension is uninstalled, it needs to be notified of the uninstall event and do some cleanup before it is removed.

Here's the scenario. We have extension B which register some Java component in extension A. So when B is uninstalled, we would like to unregister B from A. Otherwise, A would attempt to load B's Java component in the next run, when B is already removed.

In our case, A is the Java Language Support from RedHat. B is the new Java debugger from Microsoft. Both ship Java artifacts which contain the real logic. So it's very important for the registration/unregistration to happen correctly.